update API Shield changelog

Author: patriciasantaana

src/content/changelogs/api-shield.yaml

@@ -5,6 +5,11 @@ productLink: "/api-shield/"
 productArea: Application security
 productAreaLink: /fundamentals/reference/changelog/security/
 entries:
+  - publish_date: "2024-10-18"
+    title: API Shield fields in Custom Rules
+    description: |-
+      Customers can now use API Shield product feature fields in custom rules, referencing features such as [JWT Validation](/api-shield/security/jwt-validation/), [session identifiers](/api-shield/get-started/#session-identifiers), and [Schema Validation](/api-shield/security/schema-validation/).
+
   - publish_date: "2024-08-28"
     title: Increased capacity for Endpoint Management and Schema Validation
     description: |-